Tubing caliper with latch means



y 13, 1952 J. v. FREDD 2,596,924

TUBING CALIPER WITH LATCH MEANS Filed June 9, 1949 8 Sheets-Sheet 2 JOHN V. FREDD y 13, 1952 J. v. FREDD 2,596,924

TUBING CALIPER WITH LATCH-MEANS- Filed June 9. 1949 a ShetsSheet 3 7 5 5 0 mm 0 mm E JOHN V- FREDD May 13, 1952 J. v. FREDD TUBING CALIPER WITH LATCH MEANS 8 Sheets-Sheet 4 Filed June 9. 1

I JOHN V. FREDD J. V. FREDD TUBING CALIPER WITH LATCH MEANS May 13, 1952 8 Sheets-Sheet 5 Filed June 9. 1949 INVENTOR. JOHN v FREDD ATTORNEYS May 13, 1952 I 8 Sheets-Sheet 7 Filed June 9. 9

i m m m m m 3? 0 k 9 F w 9 6 M. m y 2 m 2 I J. V. FREDD TUBING CALIPER WITH LATCH MEANS May 13, 1952 8'Sheets-Shee1: 8

Filed June 9. 1949 JQHN V- FREDD Patented May l3, 1952 TENT OFFICE TUBING CALIPER WITH LATCH MEANS John V. Fredd, vDallas, Tex., assignor to Otis Pressure Control, Inc., Dallas, Tex., a corporation of Delaware Application June '9, 1949, Serial No. 97,940

The present invention relates to a device for simultaneously calipering and recording accurately the internal surface conditions of pipes, tubes and like conduits. The device has special utility in the determination of variations from the normal of internal surface configurations such as the inner surfaces of extended lengths of connected conduits, particularly oil well tubing.

It is well known that oil and gas well tubing becomes worn and corroded after periods of use, depending upon the operating conditions to which it is submitted. Many wells produce, in addition to oil and gas, salt water or water having a high acidic content which actively attacks and corrodes the tubing resulting in the formation of pits and depressions on the internal surfaces of the tubing. In addition to corrosion, scoring and wearing of the internal surfaces of the tubing is caused by the passage of well tools through the tubing and by the presence of foreign materials in the fluid flow. The indentations on the tubing walls'resulting from the scoring and corrosion are sometimes so severe that the wall thickness of the tubing is reduced to such an extent that it cannot withstand the pressure of fluids flowing therethrough or support its own weight. Consequently. the tubing becomes ruptured or parted, frequently subjecting the casing and surface connections to excessive and dangerous pressures and necessitating its hazardous removal at great cost after the damage has been done. To prevent such failure of the well tubing, it is desirable periodically to determine the condition of the.

inner walls of the tubing in order that replacements can be made or proper precautions taken to prevent any of the tubing becoming ruptured.

Calipering devices which usually involve the application of electrical circuits, are now available for measuring variations in the internal surfaces of well tubing. However, devices of this type are not especially adapted for use with well ;-t'ubing which is under pressure due to the practical difficulties incident to using cables and otherelectrical equipment which are required to effect'the recording.

The present device is entirely mechanical in operation and is so constructed that it is readily utilizable with available equipment which is customarily used in auxiliary well operations, for example, such equipment as is used in tool"f1shing, well surveying, running and pulling tubing safety valves, chokes, bottom-hole regulators, etc.

It is a principal feature of this inventionto provide a calipering device which may be lowered or dropped as a unit by a suitable wire line Claims. (C1. 33-478) into the tubing of a well under pressure and effect a continuous record of the internal surface configuration of the tubing as the device passes upwardly therethrough. After the device is removed from the tubing the continuous record is examined and from this record the extent of the defect and the exact location of the tubing lengths which must be removed and replaced are readily and accurately determined.

This is made possible by the design and arrangement of the calipering or feeler mechanism. This mechanism comprises a plurality of independently operated elements, each of which is actuated in accordance withany pit or depression which it encounters as the calipering unit is passed through the tubing. Upon the actuation of any of the calipering elements, a stylus which is positioned in recording relation to a cylindrical chart will be actuated and, consequently, each independent pit or depression is recorded. By arranging the calipering elements to be independently operable, variations from the normal inner radius of the tubing will be indicated, that is, as a pit or depression is encountered the calipering elements independently enter a pit or depression and a record is effected. The record, however, will show only the deepest pit encountered, since as mentioned before, the stylus is independently actuated by each feeler and of course the principal concern is with the worst corrosive area for a determination of tube re- 1 as a group when a joint or connection between adjacent tubes is encountered. This latter func tion of the calipering elements is very important in the practical use of this invention, since the record effected for the jointures encountered will all be generally of equal magnitude and will appear at substantially equally spaced pointson the recording chart. For example, consider a well tubing string of extreme length, such as from five to ten thousand feet, made up in thirty -foot sections and joined together by internal or external collars. As the calipering unit is passed through the tubing and the joints are encountered, the calipering elements, acting simultaneously, will be forced inwardly or outwardly as a group,- depending on whether the couplings for the tube sections are inside or outside couplings. Each time the calipering elements encounter a coupling of the well tubing the stylus member will be moved longitudinally of the .chart substantially the same distance and the indi- 3 cations on the chart will be similar and equidistant, assuming the tube sections are of the same length. Therefore, the number of sections through which the calipering unit has passed as well as the particular section or sections which are corroded or pitted can be readily determined from the recording chart.

It will be understood from the above that the calipering portion of the unit is arranged to provide two complemental functions. An operator of the instrument can caliper tubing in wellsof great depths and also determine from therecording chart, the exact location of all pits or depressions encountered within the tubing, par-*- ticularly those which may be considered hazardous to the further operation of the well tubing. It will further be seen that the calipering. unitis. designed to permit its construction to be varied for calipering different sizes of well tubing and that it is particularly adapted in its construction and arrangement of cooperating parts to. be.us.ed With. well tubingwhich. is. operated under high. pres.-,.

sures.

The tube calipering deviceof the present. in-. vention difiers from known. devices. in. that: a. stationary cylindrical chartis provided: toreceive a. record during the calipering operation and. a. helical record is effected. through. the simule. taneous rotative andlongitudinal movement-of the stylus relative to the chart.

The rotativeeffect. ofthe stylus isbrought about through the mediumof a drive wheel and two pressure wheels which are maintained. in. contact with the inner-surface of the tubing and tend additionally to. center the device therein- Suitable gearing and various other,.cooperating elements are positioned within. a.' specially. designed housing and located between the. drive wheeland'stylu s.

The caliperingelements in oneusefuhembodiment' are bell-cranklevers andare-locatedinthe.

housing above the stylus. Each has a lateral arml which extends inwardly. towardtheaxisof. the housing and a dependingarm-whichis1disposedat an angleof90 to thelateralarm. A spring is provided for each. calipering. element;- to exertpressure onthe lateral-armsandmo force the depending arms outwardly of thehousing to:

be inoperative contact with the tubing:duri'ng the calipering operation and, additionally, provision is made to maintain the caliperingelements in retracted or nonoperating position: as the device is initially. passed downwardlythrough the. tubing.

A lead screw is. provided which is non-rotatable. butis urged longitudinally of the-housing constantlyby a spring in a compartmentlocated abovethe drive wheel, and.urges a bearing surface .constantly against the low.er surfaces. of. the. lateral arms of the caliperingrelements. A. cooperating spring is positioned. above thecalie. pering elements and axially of thehousingwhichforces constantly anotheinbearingsurface axially.- of the housing against the upper surfaces of; the. caliper. lateral. arms. springs above and below. the lateral arms -.of.. the

calipering. elements provides any arrangement for. centeringthe caliper in the 1 tubing .under, all:

conditions.

In order.thatnosubstantial area ofv the..in-

ternal surface. of tubing .which is being calipered be uncalipered or uninspected, a. substantial number of the elements are utilized. It'hasbeen. found, for. example, when calipering.tubing..of.-

about three inches in diameter, that flfteen cali-..

The. pressure. of: these.

pering elements are required to caliper the complete internal surface of the tubing. This relatively great number of calipering elements requires that each be of a particular design in order that they can be carried by and disposed within a housing of sufiiciently small diameter to be passed through such small diameter tubing. The caliperingelements preferably terminateat their calipering ends in wedge shaped areas in order to reduce wear and also terminate at their inner ends in wedge shaped areas in order that these ends may. be centered and effectively controlled by the springs heretofore mentioned.

In; the drawings:

Figure 1= is a n elevation of the calipering device.

Figure2-is a partial elevation at right angles to Figure l o f section shown by lines 22.

Figure 3 is a vertical section of Figure 2 on lines--3-3.

Figure 4 is a sectional. elevation of the release assembly. and feeler, fingers.

Eigures.. ,,6, 7.:and8 are details of elementsin Figure 4.

Figures, 9 and: l0 ar e cross-sections of Figure ion lines. 9.-9, and Ill-l0; Y

Figure 11 is a sectional elevation of the release, feeler andstylus assemblies.

Figure. 12' is, an. enlarged detail in sectional; elevationof the lower half ofFigure 11.

Figures 13, 14 and15 are sectional detailsof: Figure. 12. on. lines, l 3;l3, [4-41 and I5. -|5

Figure.16 is..a sectional. detail of the, driving mechanism.

Figure. 17. is. an. enlarged detaili of'the chart member. I

Figure 18. is. a separate detail of the stylus.

mechanism.

Figure 19 is. asectional. detailof the driving ratchet assembly.

Figure.20 is a. crossesectionof Figure line.20.20..

Figure. 21 is an enlarged section ofthe lower part. of: Figure. 16.

Figures 22, 23: and 2.4.areadevelopmentand. sections of the driving'gear train.

Figures 25.and:26. are, details of theloading wheel mechanism.

The. complete calipering instrument is shown; in elevation in Figurelas it. appearsready for insertion in the tubing string to be'surveyed, Exclusive, of the top sub A;and-bottom'plug-H which .connectthe vinstrurnentto operating; lines, rods andiother tube measuring devices itcomprises six; sections, as shown, 7 which are detach: ablefrom each, other f or. adjustment; and inspec; tion purposes. The release assembly Bishoused. in, the upperv section andthreadably connects with the top sub A. Adjoining the; release assembly. B, thefeeler, headassembly C;is showndivided'ginto two parts whichenables adjustment ofgthefeeler mechanism as required under vary ing conditions. A; stylus bushing -assembly l) is enclosed in thenext lower section .whichissimilarly .readily. disengaged for. inspection and adjustment. The next lower section of :the housin marked E enclosesthechart on which the; record of the acalipering is; marked: and is. referred to. asthechartchamber. Between the chart cham-v ber. E. and the stylus driving, mechanism (3;; a. ratchet assembly sectionF-is inserted to .protect. the. driven stylus mechanism and insure accurate records. At. the .bottom, plug H.closes.the,end: of 1 the instrument housingand afiordsa .connectionfor asecondcalipering device or other;in-. strument. In describing thedetails of thesesecr.

tions, the instrument will be considered from the top to the bottom as here outlined, and the same numerals will be used to indicate like elements throughout the drawings.

Reference is made to Figures 1, 2, 3 and 4 for the details of the release assembly B and the connection between the release and the feeler head assembly C. Through a description of these figures the primary purpose of assembly B, which is to hold the feeler fingers 58 retracted until the survey is to begin, will be clearly understood. The releasing mechanism of the release assembly includes a dog 50 shown projecting from the body of section B in Figure 1. A side view of this section on lines 2-2 of Figure 1 is given in Figure 2 showing the transverse slot opening 5| in the instrument housing which permits the dog 50 to project outwardly on the opposite side. The cylindrical discs 5252 retain the dog 50 and the release link 53, connected by a flat curved spring 54, in operating position. Figure 3, which is a cross-section of Figure 2 taken along line 33,,shows the position of the dog '50, the latching link 53 and the fiat curved spring 54 as the instrument is moving upwardly in the tubing string T. The dog 50 is projected outwardly and upwardly ready to engage the joint W of the tubing string T united by collar U. One of the discs 52 has been removed in order to show the relative positions of the elements of the release mechanism.

To release the feeler fingers to operating position, the motion set up by the dog 50 engaging a tubing joint is transmitted by the release link 53 to the head 51 of the release plunger 58 which is partially shown in Figures 2 and 3 but more fully detailed in Figure 4 to which reference is now made. The release link 53 is connected to the release plunger head 51 by pin 59. The end of the head opposite the connection at pin 59 is recessed to receive a set screw 60 and is bevelled on surface 5| to clear the dog 50 after it is forced down to the unlatched position by the rotation of discs -52-52. Within the release plunger 58 the release rod 62 is fastened by the set screw 60 and extends downwardly to terminate in the head 63 which, in the latching operation, engages notches in the feeler fingers and holds them in a retracted position (as shown in Figure 11) for running the caliper into the tubing string preliminary to the surveying operation. A bushing 64 retains the release plunger 58 slidably aligned in the feeler head 65 and acts as a retaining surface for the centering spring 66. After the feeler fingers are released, the head 63 of the locking piston 62 is lifted and held in position within the centering plunger 61 with which it is in slidable engagement in the bottom section of the feeler head 65. The centering plunger is moved downwardly within the body member by the action of spring 66 into contact with the feeler fingers 6B and urges them outwardly against the wall of the tubing with equal force, thus minimizing the errors which would arise due to the center line of the caliper moving away from the center line of the tubing string.

Continuing with reference to Figure 4 and referring also to Figures 5, 6, '7, 8, 9 and 10, the feeler head 65, referred to above, and the feeler head assembly section C of the calipering instrument will be described in detail. Standard machine shop operations have been used to produce an accurate and easily handled assembly locus for the feeler mechanism as shown by the stripped down feeler head in Figure 5. The thread 69 of release assembly B engages a like thread H! on the feeler head and properly unites these two elements in operating position. The milled slots H, annular groove T5 and threaded section '90 form the basic structure to receive the feeler fingers which explore the tubing wall. Coupling with the next lower section of the caliper is facilitated by thread 95.

The machined structure of the feeler head just described, isparticularly adapted to support the feeler fingers and permit their explorations to be transmitted to a record chart. Consideration of the design andstructural advantages of the feeler'fingers will readily indicate the cooperation of the elements in this section. Figure 6 shows oneof the feeler fingers 68 which is in the form of a bell crank with an inwardly extending arm 12 and a downwardly extending arm 13 pivoted by the pin 14. These pivoting pins are end ground to abut the adjoining pins as they rest in the annular groove 15 of the feeler head and are consequently positioned securely in circumferential relation. This construction permits the use of a greater number of fingers than could hitherto be used and also makes it possible to easily locate the feeler finger pins radially and axially with extreme accuracy. The feeler fingers of the rigid surface contact type, as distinguished from the well known roller type, are especially designed to be sensitive to pits in tubing which have heretofore been missed. By eliminating the feeler wheels, the required thickness of the fingers is reduced, making a more sensitive feeler and permitting the use of a greater number of them. The contact surface 16 is a tip of hardened steel or suitable alloy, such as Carboloy, fitted into the downwardly extending arm. In general, the profile of the contact surface is designed to simulate the action of a small diameter wheel in moving into and out of corrosion pits. The distance from the center of this imaginary wheel to pivoting pin 14 i the same as the distance from pivoting pin 14 to the center of the small radius which forms the contact surface 84 of the inwardly extending arms 12, and the angle formed by the lines connecting each center with the pivoting pin is 90. This makes the radial motion of the contact surface 76 of exactly the same magnitude as the axial movement of the contact surface 84. As will be noted by reference to the several views showing the feeler linger in retracted and operating positions, the several bevelled edges perform distinct functions. The lower bevelled edge 11 is angled to permit the downward movement of the calipering device to proceed freely without catching in the tubing joints when the fingers are extended, which is required if the caliper is dropped after initial release. The upward movement is likewise freely permitted by the angled edge '18. The edge #9 is cut to lie in the plane of the housing of the instrument when the fingers are in normal contact with the tubing while the edge 80 is flush with the housing when the fingers are retracted by the release mechanism preliminary to the start of a survey. To receive the head 63 of the locking piston 62 when the fingers are latched in the retracted position, a notch 81 is ground in the inwardly extending arm 12. An additional notch 82 on the top of the inwardly extending arm 12 is designed to receive the feeler rods 83 which spring load the individual fingers and extend them to contact with the tubing. By using this feeler rod construction, it is possible to install diameter, flat-rate 7.; springs"andigairrmechanicaliadvantage :when: the feeler; fingers. approach top? dead. center; thus compensatin sgfor the. springloadfincreasezunder compression.- through the piston; and 1 connecting rod: action. However, to vkeepsthe:feeler head centered in the tubingi bore ;and;.maintain;maxi: mum. accuracy, it iS.8SS8I1tia1i thatthe: feeler point load increase slightly atja uniform;ra tejas the ,ieeler fingersmove inwardly. Optimum load on; the contact surface of; the. feeler; fingers. is thus achieved,regardless-of radiahposition; A' rounded; edge 84-1 is 1 the contact: through: which the movementyof-the;fingers is; transmitted to the stylus aWhiohwill. be discussed; later in detail;

Referring: again to; Figure; 5,; the. annular g-rOye1 -'I5 in the feeler head;& ;is;machined. to receive; the: pivoting pins: 14; whichI abut each other; circumferentially as. explained above. A retainer; ring; 85, detailed in 1 Figure 'l, with slots 85., and counter-bored aszat 8-Tl, caps;the;feeler fingers-, and; the pivoting; pins; and holds them securely. inrplace;v To hold; the retainer ring; in placaand; facilitate assembly of this; element of the 3 instrument;. a nut. 8 8;. Eigure; 8, is internally threaded at. 89 to engage, like, threads 90 on the feelerihead; Enclosing thefeelenhead assembly is a sleeve $2v which; fits into shoulder- 91l on the nut 88 as the lower support andv is received ,in aqlike shoulder 84 0f the releaseassembly. section Bit supportthe upper end. Within theenclosed space defined-by this. sleeve; and; the feeler head arehoused theffeeler; finger, activating: mechanism: and means to. adjust their operating f orce;

Returningto Figure 41 wherein these elements are'shownin enlarged detail, immediately below the releaseassembly section B and secured therebyyis; agspacer Washer. 96; which may, be varied in; thickness; to, extend ,the spacing between the release a s mbly s c on nd the f l r; he d. ssembly mechanism, to; vary; the feeler; spring compression: andjeeler pointvloading, either with orrwithout' a change 'inthe length, of the spacer sleeve;- A guide-ring 97,- retained in radial position by; a Woodruff key K, is mounted, to receive thespringguides 93; and retain the individual feeler-finger operatinggsprings93;. These guides serveas the-only means of keeping; the springs from interfering with each; other as; they are located in an annular space with only small clearancebetweenthem. On the lower-ends of the ,springyguides 9,8; the, heads 99,- .aligned. radially by. the sleeve; 92-,- abut; the lower ends of. the springs; 93-, causetheguides to move downward against the feeler-rods BS-and thus transmit the thrust -to -the feeler fingersi 6.82 as shown; This construction allows the greatest; circumference of; the. device: to be: used .for mounting of the spring, guides 98 with the maximum perimeter spacing: of the springs; In turn, this permits-the use of, springs; of larger size.v together with a greater-number of:feeler armsv The feeler rods 83 are rounded; both; atthe. top and bottom to seatginsockets lililginthe heads. 99j of-jthe spring guides and; in the. notches, 821 in. the .inwardly extendingarms 12; of; the feeler fingers; 68.

Figures-9 and complete ,the detailed descripticnof the feeler head-assemblyand are crosssectionstaken on Figure l to clearly-showthe arrangement and location of thafeeler arms and guides. The upper section shown; by Fig-ure 9 indicates the circumferential distribution of the guides 98 and the; springs 93; about the feeler head 6-5. The centrallylocated; release rod 62is also shown properly positionedrwithin the-feeler hea Figure lil is across-section taken below 8; section 9 and; demonstrates; the: positi nz i: he feeler fingersifihmboth the normali and e tended operating positions..=as;in;entermg a;pit;P.-;- This; latter cross-section is takflnzjustabove thepirotg. ing. pins.'!4;0f theieeler arm s;68 and. shows; all intersected;partsinsectionalzsymbol;

The next detailsofithecaliper; to :be considered. areithey stylus bushing; assembly D and thechart chamber section'E which; closely-cooperate,,both; internally,- and. externally; and: will be described; together; Reference made to Figure l; for: the; assembly: and; external appearance. andto zEigures 11; 12,113; lepld lfi';ITI'andJSAfor-a description. of: the-internal elements. and their: cooperation; The. stylus bushing. assembly. D threadedly engagessthreads. on. the lower. end. of 1 the feelcl. headafifitsand iszthereby properly. positionedl-ini-the assembled-iinstrument.v It will be noted in Figure 1 that: all threaded. members are provided with shallow, holes 1 to receive spannerewrenches .for. making andibreaking; the jointses: required .for. complete. assembly. and; disassembly; Figure- 11. givesthe above threaded joint-in detail and jurtheh-ShOWS the slip jointlili of the chartichann. berzclosure I04 whereitijoinsthe stylus bushin assembly: Chamber. screws 62; made from halide ened; fine-thread socketset sorewswithl heads taperedidown. to fittightlydnto holesin' the chart chambers closure, completev this. connection. and prevent disengagementduring operation. Azprss: sure relief hole I 83 is drilled throughxthechart chamber. closuretl Mite permit. uninterrupted: operation of the chart. chamber. elements during; the survey which normally. takes: place under pressure conditions. Reference torFigure 16f shows. the lower end ofthechartchamber closuresto be .a. duplication of the upper. end just describedso that in assembly: either end' may. be placed upward and no mistake is possible.

The-sections of r the calipering device now under discussion are. seen more clearly in Eigure. 12: Startin atlthe top of] this figure with; the .feeler fingers: 68'; which have" been. describednabova in detail; the rounded edge 8410f the under. side-of the-inwardly extending armsfll are normallyJ-in contact: with. the .head: end; I 0.5.1 of the 1 stylus rod H16: In. this view. one-.of thesfeeler. armsl has moved outwardly to at greater: degreethan. the other armas-on entering a pit :or depression and islpressing the stylusrod. downwardly. A; slot i 01 is let .intothe =stylus.;rod l 116i to passthe; pin I 518i; mounted: in the adjustable member-[0910f the stylus bushing, which prevents. rotation i of the stylus .rod yet permits-the desired axial movee mentlset upbythe feelerfingers. A stop l lflzabuts the. end of: the adjustable bushing member toprevent. the upper edge of the stylus rod.- slot. from strikingiand shearing. the pin I08; Asdesigned; the stopialso prevents thepin from-slipping out; thus preserving its primary. function, namely. to prevent rotationofi thestylus rod; Another sl'ot H l inthelowen endrof. the rod l 86 cutto .receive the millediendiof'the stylusleadscrewl l4; permitsready disassembly. without disturbing-the fixedi ratchet I I2 of; the stop clutch H 3 :and: fur.- ther prevents the stylus lead; screw, from rotating... The maximum diameter to which-the feeler armsnnay: be extended is adjusted; axially :within the-deviceiby. the adjustable member Hi9:v which threadedly engages the stylus: bushing D; as shown. The .lockingnut H5; preservesthisiads J'ustmenttonceitis made. The set-screw; l lfizre tains the: ratchet. I I2 infixedipositiom Having. described. the; stylus lbushingr: assembly D. downrto; the stop-clutchitis. logicahfromthe joints and physical construction to consider the elements immediately below this point as parts of the chart chamber section E. Starting with the internal construction the stylus rotating mechanism extends downwardly from the movable ratchet I I1 of the stop clutch H3 of Figure 12 to the driven ratchet H8.of the driving'clutch H9 in Figure 16. The assembled detail of this part of the mechanism is illustrated in Figure 1'7 and is separately shown in Figure 18. Sectional views, necessary to a complete understanding, are given in Figures 13, 14, and 15. With reference to Figure 17, the stop clutch H3 includes a fixed ratchet H2 and a movable ratchet I I 1. Attached to the movable ratchet are the drive rails I20 which extend downwardly to engage the driven ratchet H8 of the driving clutch H9. These driving rails are suitably fastened on both ends to the ratchet as shown in this figure. The nonrotatable stylus lead screw I I4 is positioned through both clutches and is supported by the conical bearing I2 I. A stylus I22 is housed in the stylus holder I23 designed as a travelling nut and slotted at I24I 24, asshown in Figure 15, to receive the drive rails I20 which rotate it about the lead screw I I 4. Forming a part of the travelling nut I23, a threaded extension I25 extends the threaded contact area over an added length of the lead screw for better operation and control. The stylus lead screw I I4 is centrally positioned in this figure which also discloses the rela-- tion of the stylus holder parts together with the stylus spring I26 used to urge the stylus into contact with the surface of the chart I21. A single coil spring is used to load the stylus point more uniformly than could be done with a small diameter spring. Moving upward on Figure 12 of which Figure is a cross-section, another section Figure 14 shows the movable ratchet H1 of the stop clutch I I 3 with the lead screw H4 passing through the center. The assembly of this clutch element and the drive rails I 20, considered with the elevation of the stylus driving mechanism assembly as shown in Figure 18, clearly illustrates the arrangement of these elements. A section of the upper chart retainer I28, slotted at I29 to permit contraction and expansion to position and fasten the chart I21 in place, is included in the sectional View of Figure 14.

The circumferential dimension; of-the chart retainer I28 is such that, when in place as shown in Figure 14, the slot I29 is of sufiicient width to cooperate with pressure relief hole I03 (see Figure 12) in chart chamber closure I04 to permit pressure equalization throughout the instrument during operation under pressure conditions. When the caliper is assembled care must be taken to locate slot I29 opposite hole I03 in order to permit the aforesaid pressure equalizaion.

. Enclosed within this section E are the chart I21, chart retainer I 28 and a similar retainer 3I in the lower part of the chart chamber and are clearly shown in details of Figure 17. The upper and lower chart retainers are bevelled on the edgetoward the chart with a, shoulder at points I32 and I33 respectively to wedge the chart in place and prevent any movement of the chart surface during the calipering opera-- ratchet "of the "driving clutch H9. The internal and externalsurfaces of the sleeve being smooth,

'nozintendedmotion of rotation or retention are transmitted to it by the elements adjacent thereto. To keep the disengaging device from falling out of the driving clutch when the caliper is disassembled, a retaining ring I35 is fastened 'on the upper end. The length of this device is suficient to extend through the upper ratchet of the clutch H9 and into the lower ratchet MI in order to provide for transmitting pressure to the lower ratchet at the end of the stylus travel as will be fully discussed in describing the operationof the caliper.

At the upper end of the ratchet spring assembly F, adjoining the lower end of the chart chamber closure E, are a slip jointv I36, chamber screws I31, and a pressure relief hole I38; all similar to the structure and like elements described for Figure 11 and, as pointed out there, intentionally so constructed to prevent mistakes in assembly. The O ring I39 is set into a groove I30 to retain the lubricant with which the chart chamber is filled.

Continuing downward in the examination of the details of the caliper, the ratchet assembly F is the next section to be detailed and. is located externally in Figure 1 and internally in Figure 16 which sectionalizes the elements and indicates theiroperating relation. For the description of these elements general reference is made to these two Figures, 1 and 16, and special reference is made to Figure 19. In this latter figure, and continuing downward from the slip joint [36 by which the. chart chamber section E and the ratchet spring assembly F are joined, the housing I40 is designed to receive the elements which transmit rotary motion to the stylus. The driving ratchet I4I of the driving clutch H9 comprises a reduced tubular extension I42 which terminates at the upper end with the ratchet teeth and extends axially through the bore I43 in the slip joint end of the housing I40. Equi-spaced holes I44-I44-I44 are drilled through this end of the housing, as shown in section in Figure 20, to permit the transfer of lubricant between the chart chamber section and ratchet spring assembly. The lower end of the driving ratchet I4! is an enlarged bored section I45 telescoping with the driving member I46. In the walls of the section I45, longitudinal slots I41 are cut to slide over and engage pins I48 on the driving member I45 insuring rotational movement of the driving ratchet. A ratchet spring I49 envelopes the driving member I46 and urges the driving ratchet I4I upward to engage the ratchet teeth with the driven ratchet H8. Enclosed within the member I 46, the stylus lift spring I50 exerts an upward pressure on the stylus lead screw plunger I5I which supports the stylus lead screw H4 in the conical bearing I2I. The section of the plunger adjacent spring I59 contains the upper section of a fluid flow control I52 which, cooperating with the adjustable screw stop I53 mounted in the stand I54, cushions the downward stroke of the lead screw H4, by decreasing the flow path of lubricant filling this part of the device. The pin I55, placed diametrically across the flow control I52, limits the downward movement of the lead screw after the speed of travel has been decreased by the upward movement of the lubricant around the screw I53 and through the controls. The adjustable screw stop is adjusted to halt the downward travel of the lead screw only after theifeeler arms have beenipermittedto reach their. maximum, outward, movement; The i base 11 4-56 ---of -the -=dr-iving member i I46 is f flanged 1 to support I the spring- 149 ----and is machined down --to-ashaft -=I-51 with-a conical bearing 153 .7 At the lower -end of l the housing 1 40 "the thread i fificonnects the ratchet-spring assembly-section F-to the drive -mechanism" section G.

-Deta'i-ls ot the flanged base 156 of -t-he driving member Me -and *thebearing-plate l 58, drilled at "Hi "to per-mit lubricant to pass downward, "are repeated in-Figure =2 1 whieh showsthe details of the driving mechanism insection 'G, 'Theupper threaded-end'i-fil adapted to-engage the threads of "the section 5 above, is counterbored to form the'gear chamber -I62. Supported-by the hearing 1'63, theshaft-i-lil of the driving member 'I4"51iis"fittedwith the gear 154 wh-i'ch -for'ms part ofagear train fully developed in Fig-ures 22 and '23. By reference'to'these'figures as -well-as Figlure-21;. now under 'discussion,-'-it will'i-be-understood how the rotary motionof'shaft 1 65; trans- .mitted by gear 166 Which i -keyed-thereon,-is passed" throughgeari 61 to shaft JBS'amclt-hence through gear; 'IEQrto gear-1'64. on the shatter-the drivingmember. A'fuller understanding of the ,origin of the rotary, motion; which is imparted to the shafttSBrand setsthe gears "in :motiop, .willmbe understoodby-reierring to :Figure"24 -in W conjunction .with -Figure -"21. The driVe' Wheel l'l.0,:whichis rotatedbycontact with the-inner wall of the tubing string asithe' calipering instru- ;ment is raised orlowered, is'rotatablygmuunted ,ona fixedvshaftflli. "Interposed between the rotatable drivewheel andthe solid body portion 113 of the drive mechanism section G, 1 through which the ;lateral:slots H4 .and'ifi are imachinedjto mount the worm gear and the-drive wheel respective y, the brass 'washer 112 "is mounted to reduce wear. "The worm gear-lfli V is. secured .tothetdrive wheeliin-t-he slot; I'M-and .meshes with theworm wheel I'H which isjkeyed to the bottom of the shaft 1'65. "A sleeve 1 H8, splitpn the line'of' the edge'of'theidrive wheel 1'10 v.to lpermit'its'free rotation,"is'=fittedover the slotted; portion ofthe solidbody; I13 toclosethese assembly openings. "In'theloweripartofthe drive mechanism .bo'dy 11:3,.intersecting slots I T9'l|9 are milled to receive the'it.woloadingwheels l'8l) l'80 as shown inliigures 21;and--25. These wheel are bevelled on-,the-chntactperipheries to conformito'the' arc of the; inner-wall of i the-tubingr stringiandithus "insure maximum contact area sand constant pressure. Each "of-{the loading. wheels "l'8-0i8"9 'is' rotatablyjournaled in a loading arm of the .design SllOWIlf in Figure "26, and Leach 'loading' arm is, 'in jiillll'l; pivota-lly mounted within the intersecting slots. '"-As-'wi1l be; seen ;in Figure '26, each xloading arm 48! 'is slotted at m2 providing a space between-upstanding walls"|83-'-'i83 whichireceive a loadin whee1 180. ';The 'loading wheel is "rotatably' mounted ona shaft I84 vwhich extendsthrough theih'oles l-fifipf the loadinglarm. IjBetaining each loading arm place within the slots l 55-; I 1.9, a pivot pin L86 .passes through the hole it? in the loadinguarmsand the holestliififilaaldrilled :in the body-, I413. flhe bottom-lofgeach loading arm is cut vto rovide-shoulders i 89 and [93,1318 formal-spring pressed upwardly by piston -l9i which fits into the drilledv hole 192 in the bot- 111.0111 .ofthe :drive mechanism :body lis'iand the latter actingasra-Icheck against unrestricted outward-movement of;.thez-.l0adingarm. The bor 55 5-3 iw-ithin;thepistonlcontains az sprin {:24 :which 'isrthe' activatonior'ithepiston and is maintained ":12 a under compression. :by::;the plug 13.5 zfthreaidedly engaging the, lower .en dcof:the: zbodyrzmemben .1113. Retunning to :Eigure :i 16 to-.'c.omplete1the Ide- .-wsc'ription; the :plug 3H :isshown: asicentra'llytidrille'd 5 and tapped." at 18.61: to; receivesadditionalz toblsmr another calipering: instrument if;v itxisidesiredito usemthese devices in tandem. aAhole E :l 9 li -may; be drille'di through the plug; .195 totadmit wellifiuids to the lpistonachamber if desired.

It is believed .the detailed description ,a'boveiwiil fibe sufliciently understandable tozthose versedrin -the-' art to visualize theloperation ofither-xievice. However, alas .the cooperation :ofttheelemenis -abovedefinedagives .allong sought ioniresulttmith a 'high idegreeaof accuracy and .exceptionalzzper- -20- pressures if necessarynwithoutizkilling the well,

' pressure is hecessary. Amorrg:the items 'used ior A such equipment may benamed hoisting-and reel- "ing :machines, depth -ga-uges, high pressure "stunting boxes, "pressure chambers known ithe trade: as f lubrica-torsj gate valves: and; :the' like,

" which'are merely-referred to -here a wthey form 4 "figure 1 and 'make-a'thorough' cheek oft-he mechanism for undue wear-and operability. This is "a i feature of the 'device and "requires wery' t little -time-and a -min-imum of =-standa1 d-tools. All .partsof the apparatus are-"readily acoessible and .-=-easily. adjusted orreplaced. The usual prepara- '-=55-iaee to: be marked-by the stylus- 1 z2-is insented -i-n-Ift1'1e chart chamberqau'd held seeurely'by upper retainer I:2 8 andthe lower retainer 13 I as shown in -Figure? 12. i'I-hese retainers position the-chart -axiallyand hold'it flat against the chambenwall,

preventing any movement of the chart. Toplace the stylus in a.v position ready for-operation;- the stylus holder. is rotated. until it is at' the topof the lead screw and the upperl'edge'bf the 'chart, also illustrated in Figure. 12,- andtthe stylus operating-mechanismeis put balekiinizthe chfli t her: being :surez-the lead screw: and-fdriving'bluteh are :properly positioned. ZLubricatingmil -is then poured=intoithe: chart chamber until-ithe ratchet "assembly: andv chamber (are filled sto keep swell ffiuids .aa-ti high pressures from :afiecting: the Jinby using chamber screws I02 which are tapered, socket setscrews. On disassembly they are rotated into the stylus bushing body and on reassembly they are backed out after the joint is united to fit firmly in holes drilled to receive them in the chart chamber closure I 3 (Fig. 11). As the full well pressures are admitted to all parts of the caliper mechanism, including the recording stylus and chart, and equalized throughout by means of the lubricant filling these spaces, packing glands and gaskets with their inherent frictional drag are. eliminated. The result of the equalization and balancing of the well pressures is that the stylus follows the smallest variation of each feeler arm as they explore the inner wall of the tubing string. The lubricating oil is retained within the caliper by the synthetic rubber O ring gasket set in the groove at the lower chart chamber joint positioned there to prevent leakage. The feeler fingers are then pressed into the retractedposition and held there while the head of the release rod 63 is lowered into locking engagement with the notches provided in the feeler fingers by rotating the cylindrical discs 52 which also places the dog 50 in the locked position. The feeler fingers being urged outwardly by the piston like action of the feeler rods 83, as shown in Figure 12, press against the release rod head 63 and remain locked until the release rod is lifted. The caliper is now ready to survey the tubing string of our example.

By arranging the pressure retaining equipment enumerated above, and properly mounting it on the tubing string at the top of the well, the caliper is introduced into the tubing string on a wire line without pressure loss. The caliper is then lowered to the desired depth, the feeler fingers remaining in the retracted position, as described above, during the entire descent. The dog 50, projecting outwardly of the release assembly body and upwardly as shown in Figure l, is held in light engagement with the wall of the tubing by the action of spring 54 and has sufficient movement to pass freely downward without disturbing the release mechanism. It is retained in this locked position by the load of the feeler fingers pressing against the head of the release rod. On reaching the desired depth, upward movement of the instrument engages the dog 50 in the first tubing joint above the stopping point and causes the release assembly to function, starting as shown in Figure 3 and ending as in Figure 4, lifting the release rod 62 from looking engagement with the notches 8| in feeler fingers 68, permitting them to spring outwardly to contact the tubing walls and beginthe calipering operation. The pair of discs 5252, having rotated to lift the release rod, drop the dog downward to lay on the bevelled head of the release plunger where the fiat release spring 54, having'travelled overcenter, is desired to keep the dog confined within the release assembly body. At all times, the centering plunger 61 is urged downwardly by the compressed centering spring 66, restrained in'upward movement by the bushing 64 above, to constantly engage the upper edge of the inwardly extending arms 72 of the feeler fingers 68. The constancy of this action by the plunger is illustrated in Figures 4 and 12 where it will be noted that the only time this is not true is when the individual feeler fingers separately follow pits P. This equal pressure on all the feeler fingers, under normal conditions and on the greater numberwhere pits areen- 1'4 countered, centers the caliper within the tubing string and minimizes error in the charted record which would otherwise arise.

In addition to the uniform spring pressure of the centering plunger on the feeler fingers, each finger is separately actuated outwardly by the feeler rods 83 which transmit the pressure of the spring guides 98 to each of the fingers separately. The outward movement of each individual finger is limited only by the tubing wall. The caliper is adjusted so the extreme diameter reached by the fingers is the same as the inside diameter of the tubing couplings or collars U. This setting is large enough to indicate complete penetration of the tubing by corrosion and serves as a reference in making an accurate interpretation of the actual depth of corrosion as indicated by the chart. Also, this setting is small enough to permit easy entry of the caliper into the surface connections of the Well and to travel downward through the tubing couplings if the feeler arms are not in the retracted or locked position, as required in repeating surveys over limited tubing lengths. The ideal feeler finger loading is the minimum loading attainable which will minimize the Wear on the feeler finger contact surface I6 and possible damage and yet produce an accurate chart if only one feeler finger moves out to its maximum travel. An individual feeler operating spring 93 should be strong enough to move its feelerfinger firmly out to its limit of travel while at the same time depressing the stylus lift spring I50 (Fig. 16). In turn the stylus lift spring must be of sufficient strength to support the lead screw I I4 and stylus holder I23 and keep the head of the stylus rod I 05 in continuous contact with the feeler fingers even when the feeler fingers are moving into and out of corrosion pits and tubing collars at fast calipering speeds. The feeler spring compression and consequent feeler finger loading can be adjusted by changing the thickness of the spacer' washer 96 and the length of the spacer sleeve 92 or either.

During the downward movement of the caliper in the tubing string, the loading wheels mil-480 and the drive wheel I10, Figure 16, are in operating contact with the tubing wall and rotating at a speed commensurate with the rate of movement downward. The direction of rotation of the drive wheel is clockwise when viewed as in Fig. 16 and is transmitted through the worm and worm wheel to the gear train and thence to the shaft I51 which rotates the driving member I46 and through it the driving ratchet I l! Centering of the caliper within the tubing string is facilitated by using two loading wheels and pressing these outward to contact the tubing wall by a single spring and plunger acting as a unit on both wheels equally. The driving clutch H9 is designed to cooperate with the stop clutch H3 (Fig. 11) so as to hold the stylus. rotating mechanism motionless as the caliper moves downward. Consequently, no trace is made on the chart at this time. As the caliper is moved upward and the release operates, freeing the feeler fingers, the rotary motion of the drive and loading wheels is reversed. The clutches reverse their operation also, the driving clutch ratchets engaging and the stop clutch releasing the ratchets. A rotary motion is thus imparted to the stylus holder by the drive rails I20, Figure 17, and the stylus scribes the record on the chart, moving vfrom the top of the chart downward. As'the lead screwis fixed aga nst. r ta i the y us 122 stylus is scribing on the chart.

acac a-2a scribes a 'helix'in descending along the lead screw thread. The scribed helix haS th'esa-mepitch as th lead screw, with the result that the chart shows a series of parallel lines, equally spaced apart which aids in visually translating the survey. Thehorizontallscale of the chart is selected to provide maximum footage per chart while retaining clarity and to distribute tubing joint interruptions horizontally, and may be varied by changing the gears. In having thestylus move over-the :fixed chart, many more thousands of feet of tubing can be calipered'at one time than if the chart moved andthe stylus were stationary within the samedimensional limits -.of the chart chamber.

The helical movement of the stylus .is interrupted by the action'of the released feeler fingers which are now exploring the inner wall of the tubing for pits and joints. A pit in the tubing permits'one'ormore'of the feeler fingers tomove outward, Figure :4, and at the same time, to press fdOWI'IWaIdly-OII-the stylus rod [06. It will be noted that should two or more -feeler fingers move outwardly at the same time, the eflectof that which moves out the greatest distance is alone transmitted to the stylus rod. This reveals the locus and'measurenient of the greatest defect and is therefore a measure of the true damaged condition. The sum of the depths of the pits, depressions and joints, is never measured by this device. As the-stylusrrod is moved downward, this motion is transmitted'to the nonrotatable lead screw with whichit is in contact, Figure 11, and interrupts the helix which the the feeler fingers detailedabove causes the-stylus to' move away from the basic helical path the same amount-as thefeeler arms move outwardly. The resulting log, when the chart is removed from the caliper and'spread out fiat, is a series of parallel lines which show at true scale the maximum outward feeler movement at any instance during a calipering passage. The spacing of the lines, determined by the pitch of the lead screw, permits visualexamination of the survey and exact measurement of the corrosion pits. For examplaif the pitch of the lead screw were .050 inch, whichis '20 threads to the inch, and the trace-of a pit'moves up three lines, the pit would be .150 inch deep. Tubing ,joints show clearly as a series of practically regular interruptions for standard length tubing and 'are readily identified for any length tubing. The chart lines will'vary from-almost straight "to very jagged, depending on the severity oithe corrosion. .The .lead screw, which :receives 'the.:axia1 motion from the stylus rod, isasupported bynthejplunger [5L as shownv in Figure 17. A iluid'flow'control !52 is housed in the lower part 'ofthe plunger which, operating in the lubricant filling this part of the device and cooperating with the'adjustable screw stop E53, restricts the travel of the lead-screw to theeffective limit and produces a clearerchartrecord.

A particular advantagev of thedisclosed device resides. in the-ability to rewaliper a specific length of tubing without removing the device ,from :the string for re-setting. Within the limits of the chart space, readings maybe repeated .on a particular section of tubing as desired. It has been seen above that the calipering operation is'performed only as the instrument zmoves upward in the string :and that whenmoving-downwardly the. clutch arrangement :is :designed '-.to prevent the rotation :of the stylus lholder. "Consequently,

The design .of

31-6 a length of tubing may be. surveyed bythe upward movement 'of the caliper and -re-surveyed .until the chart is exhausted by dropping it .down to :the point of beginning and againsurveying by moving it upward. The release mechanism, having once been unlatched, is not rset-againbut presents no difficulty as thedogis dropped down and readily-clears the tubing joints. The feeler fingers also clear the obstructions in .the' tubing string due to the several bevelledsurracesmhich have been fully described.

Should the instrument be operated beyond the chart limits, howeventhe record=alreadyobtained is preserved sunmarred by the operation-pf the disengaging device 134, shown in detail in Figure 19. All recording action on the chart requires that the stylustrotate and move downwardly :on the lead 'screwwhich is secured against rotation, but-.move'a-xially inlresponse to the 'ieeler finger action, as described. Consequently, the survey will ultimately move the stylus holder to .the bottom of the chartregardless .of whether the run is continuousor'repetitious :as the clutch arrangement prevents the upward movement of the stylus on the lead screw even though the drive wheel is responsive to both 'upward .and downward movement. Figure 1'7- shows the disengaging device -l34 in enlarged detail and-positions itin cooperating relation with theelements of the device which activate it and :upon which it operates. The rotary motion-of-the.driverails I29 moves thestylus holder -l23 down-wardonthe lead screw IM during the scribing :operation until the bottom 'of thechart IZ-I -is reached. .At this point, the bottom .-of .the stylus holder J23 engages the :top -of'the disengaging device I 34. Continued rotation moves the stylusholder further down on the lead screw and presses with increasing pressure on the disengaging device until it forces the driving ratchet UH awayfrom contact with the driven ratchet M8. The driving mechanism is then free to rotate without transmitting motion .to the stylus driving mechanism from which it has been disengaged. The downward thrust of the stylus holder .istrans- 'mitted to the .lead screw with which .it .is threadedly engaged and exerts an .equal upward thrust through the leadscrew to the stylus rod 106, evident from an inspection .of Figure .11,

and, in turn, exerts an upward .force on Lthe'feeler fingers causing them to retract .sufilciently to withdraw from the tubing wall and "facilitate removal from the string without unnecessary wear.

The surface operating crew keeps a running .tally of the number .Of .ieet of tubing through which thesurvey is made by upward movement .of the caliper. The fixed-measurements of the chart length and'lead screw pitch being known, the number offeet of tubing which'can be calipered on one chart'is readily determined. The survey having been made, the caliper is withdrawn from the tubingstring in reverse operation to that described for starting the operation. The chart is' release'drfromthe chartch'amber and spread"f0r study. Photostats are readilymade 'from the chart, 'and enlarged if desired, 'for'extensive interpretation and inclusion in survey reports.

The example selectedfor disclosing the "operation of the caliper considered a well under pressure in which the tubing string was the object of thesurvey. This :is .notthe limit of the operaurinal-"possibilities of .this -idevi'ce, and 'is not :sc-

intended; "The calipering instrument, as here disclosed, is' fie-xiblein-applicationand may readil-y-be'used to survey any conduit, pipe or-tube in any position and under conditions ranging from atmospheric to very high pressures. Neither is the size ofthe-instrument a-controlling factor, but maybe increased or decreasedto meet specific conditions andwill operatewith equal facility and-accuracy; It is;- therefore; the intention ofthe inventor, to include :within the scope of this disclosureall devices falling-within the spirit ofthe invention, as well asthe letter thereof,

limited onlyby the'appended claims.

'I'he arrangement herein dislosed of a-fixed recorder member'and a movable stylus member,

with-drivingand transmission means for effect--- ing simultaneous rotation and longitudinal move- -ment of the stylus member, is not herein claimed as that constitutes subject matter o'f-my co-pendin'g application, Serial No; 184,497, filed September' l2, 1950, which is a division" of the present application.

-I claim:

1. In an internal tube wall caliperingdevice adapted to be passaged through successive tube sections joined by couplings, the combination comprising-an elongated housing, a" plurality of calipering members mounted for lateral movement between said housing and the tube wall being calipered, said calipering members each having an inwardly extending part and a retractable outwardly projective part, resilient means for urging said retractable parts toward contact with the tube wall, latching means adapted to engage said inwardly extending parts and thereby maintain said outwardly projective parts retracted'in opposition to said resilient means dur- ,.ing passage of the, device in a non-calipering i direction, an. outwardly, projective dog pivotally ;,mounte,d.in the housing, means for resiliently .urging theprojective end of the dog outwardly toward contact with the tube wall, said end when in projected position being adapted to slide across .1 said couplings as the. device isipassaged in ainoncalipering .direction and to engage adjacent a coupling upon passage in theopposite direction,

' adapted to be passaged through successive tube sections joined by couplings, the combination comprising an elongated housing, a plurality of bell crank calipering members mounted for lateral movement between said housing and the tube wall being calipered, said calipering members each having an inwardly extending arm and a retractable outwardly projective arm, resilient means for urging said retractable arms toward contact with the tube wall, latching means adapted to engage said inwardly extending arms and thereby maintain said outwardly projective arms retracted in opposition to said resilient means during passage of the device in a noncalipering direction, an outwardly projective dog pivotally mounted in the housing, means for resiliently urging the projective end of the dog outwardly toward contact with the tube wall, said end when in projected position being adapted to slide across said couplings as the device is passaged in a non-calipering direction and to engage adjacent a coupling upon passage in the opposite direction, and means actuated by such engagement for simultaneously retracting said dog and releasing said latching means for engagement with the inwardly extending-arms of said caliperingmembers.

' 3. A device according toclaim 2 wherein the means that is actuated by engagementof the dog comprises a. rotatable member to which said dog is pivotally connected, and linkage pivotally connecting said rotatable member with said latching means. f

4. In an internal tube wall calipering and recording device. adapted to be passaged'through successive tube sections joined by coupli'ngsand comprising an elongated housing carrying calipering means mounted for lateral movement between said housing and the tube wall beingcalipered, recording means and mechanical actuating rality of hell crank calipering members pivoted adjacent the periphery or the housing and each having an arm inwardly extending toward abutment with said common actuating means and a retractable outwardly projective arm, a plurality of resilient urging means'within the housing located adjacent its periphery, an actuating member pivotally engaged at each end thereof "and slantinginwardly from eachurging means to the corresponding calipering member inner arm, latching 'mean'sadapte'd to engag said inwardly extending arms and thereby maintain said'outwardly projective arms retractedin opposition to said urging means during passage of the d e'vice in a non-calipering direction, a dog pivotally mounted in the housing and projective outwardly thereof, means for resiliently urging theprojective end of the dog outwardly toward contact with the tube wall, said end being adapted to slide across said couplings when the device is passaged in said non-calipering direction and to engage adjacent acoupling upon passage in the opl 'ojsite direction, and means actuated by such' engagement for simultaneously retracting said dbgfrom the tube wall and releasing said latching means from engagementwith the inwardly extending arm of said'calipering members.

5. The combination defined in claim 4 wherein each of said inwardly extending arms has a notch at its inner edge for reception of said latching means and another notch for pivotal reception of said actuating member, and wherein the means that is actuated by engagement of the dog comprises a rotatable member to which said dog is pivotally connected and linkage pivotally connecting said rotatable member with said latching member.

6. In an internal tube wall calipering device adapted to be passaged through successive tube sections joined by couplings and comprising an elongated housing carrying retractable calipering means mounted for lateral movement between said housing and the tube wall being calipered, the improvement comprising latching means adapted to maintain said calipering means in retracted position during passage of the device in a non-calipering direction through the tubing, an outwardly projective dog pivotally mounted in the housing, means for resiliently urging the projective end of the dog outwardly toward contact with the tube wall, said end when in projected position being adapted to slide across said couplings as the device is passaged in a noncalipering direction and to engage adjacent a coupling upon passage in the opposite direction, and means actuated by such engagement for simultaneously'retracting said dog'and releasing said latching means.

7. A device according to claim ,6 wherein the means that is actuated by engagement of the dog comprises a rotatable member to which said dog is pivotally connected, and linkage pivotally connecting said rotatable member with said latching means.

8. In an internal tube wall calipering and recording device comprising an elongated housing carrying retractible calipering means mounted for lateral movement between the housing and the tube wall being calipered, the improvement wherein said calipering means comprise bell crank calipering members pivoted adjacent the periphery of the housing and each having an inwardly extending arm and a retractable outwardly projective arm, a plurality of circumferentially spaced urging means, one for each of said calipering members, located adjacent the periphery of the housing, and an actuating member pivotally engaged at each end thereof and slanting inwardly from each urging means to its corresponding calipering member inner arm.

9. In an internal tube wall calipering and recording device comprising an elongated housing carrying retractable calipering means mount ed for lateral movement between the housing and the tube wall being calipered, an improved calipering means assembly which comprises a body member constituting a portion of the housing and having an extension of reduced cross section positioned longitudinally within the housing and forming therewith an anular space, said body member havig a plurality of circumferentially spaced slots and a circumferential groove adjacent the junction of said body member and its extension transversely intersecting said slots, bell crank calipering members having inwardly extending arms and outwardly projective arms retractable through said slots, pins at the pivotal loci of said calipering members positioned within said circumferential groove in abutment with each other, a plurality of urging means, one for each of said calipering members, located within said annular space, and an actuating member pivotally engaged at each end thereof and slanting inwardly from each urging means through the corresponding slot to the corresponding caliper member inner arm.

10. In an internal tube wall calipering and recording device comprising an elongated housing carrying retractable calipering means mounted for lateral movement between the housing and the tube wall being calipered, an improved calipering means assembly which comprises a body member constituting a portion of the housing and having an extension positioned longitudinally within the housing and forming therewith an annular space, said body'member having a plurality of circumferentially spaced slots and a circumferential groove adjacent the junction of said body member and its extension transversely intersecting said slots, bell crank calipering members having inwardly extending arms and outwardly projective arms retractably operable in said longitudinal slots, pins at the pivotal loci of said calipering members positioned within said circumferential groove in abutment with each other, a plurality of urging means, one for each of said calipering members, located within said annular space, and an actuating member extending from each of said urging means to the corresponding caliper member inner arm.

JOHN V. FREDD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 713,784 Mellor Nov. 18, 1902 1,339,955 Hardel May 11, 1920 1,409,304 Loomis Mar. 14, 1922 1,676,848 Au July 10, 1928 2,040,501 Sawford May 12, 1936 2,102,080 Kinley Dec. 14, 1937 2,322,343 Brandon June 22, 1943 2,392,357 Bays Jan. 8, 1946 2,518,663 Chaney et a1. Aug. 15, 1950 

